The present invention relates generally to a reciprocating piston compressor assembly and, more particularly, to an improved valve system for such a compressor assembly, wherein a suction valve assembly associated with the piston interfits with a discharge port associated with the valve plate and cylinder head to reduce reexpansion volume in the cylinder.
In a typical reciprocating piston compressor, a cylinder is defined by a compressor crankcase and a piston reciprocates within the cylinder to compress gaseous refrigerant therein. In a compressor to which the present invention pertains, the piston comprises a piston valve assembly wherein the suction valve is operably mounted on the piston head to receive gas through the piston from one end of the cylinder and compress the gas in the cylinder for discharge out of the other end. A valve plate is mounted to the crankcase so as to close the top of the cylinder. The valve plate includes a discharge valve assembly operable to discharge gas into a discharge space defined by a cylinder head cover mounted to the crankcase with the valve plate disposed therebetween.
The present invention is particularly applicable to a scotch yoke compressor, wherein a plurality of radially arranged pistons are drivingly connected to a crankshaft by means of a scotch yoke mechanism within a suction cavity. An example of a scotch yoke compressor is found in U.S. Pat. No. 4,834,632 assigned to the assignee of the present invention and incorporated herein by reference.
The aforementioned patent discloses a scotch yoke compressor having piston suction valve assemblies wherein a valve retainer is attached to the piston by means of a centrally located fastener, the head of which is received within a recess in the valve plate to reduce the reexpansion volume. Such an assembly does not ordinarily reduce the reexpansion volume attributable to the discharge ports. In U.S. Pat. No. 1,764,655, a suction valve retainer is centrally mounted to the flat top surface of the piston, and extends therefrom and is received within a central round discharge port in the valve plate.
In prior art compressors having both discharge and suction valving associated with a compressor valve plate, it is known to use a piston having an annular upstanding portion on the piston head that fills a corresponding annular discharge port when the piston is at top dead center.
It is desired to provide an improved valve system for a compressor requiring a valved piston and having discharge valving associated with a valve plate, whereby reexpansion volume associated with a discharge port in the valve plate is minimized.